Impact of transdermal flunixin administration on serum prostaglandin E2 and cortisol concentrations in piglets following castration.

Objective: To assess the effects of transdermal flunixin administration on serum prostaglandin E2 (PGE2) and cortisol concentrations in piglets undergoing castration.
Animals: 104 litters with at least 4 male piglets/litter.
Procedures: Litters were randomly assigned to 1 of 4 treatments: transdermal flunixin (3.33 mg/kg) administration followed by surgical castration (CF; n = 28), transdermal flunixin administration followed by sham castration (SF; n = 26), application of physiologic saline solution followed by sham castration (S; n = 26), and application of physiologic saline solution followed by surgical castration (C; n = 24). Blood samples were collected 24 hours before and 1, 4, and 25 hours after castration or sham castration.
Results: Serum PGE2 concentrations for piglets in the C and CF groups did not differ at any time. Piglets in the S group tended to have higher serum PGE2 concentrations 1 hour after sham castration compared with piglets in the SF group. One hour after the procedure, piglets that underwent castration had higher serum cortisol concentrations than did piglets that underwent sham castration. Piglets in the CF group had higher serum cortisol concentrations than did piglets in the SF group 4 hours after the procedure, but serum cortisol concentrations did not differ between the C and S groups.
Clinical Relevance: Further studies are needed to explore dosing regimens, including effective doses and administration frequencies, and the pharmacokinetics of flunixin following transdermal administration in piglets undergoing castration.